Cyclic perfluoroaliphaticdisulfonic acid anhydrides

ABSTRACT

Cyclic perfluoroaliphaticdisulfonic acid anhydrides, sulfonamide derivatives thereof, a process for making the same, curable compositions containing cyclic perfluoroaliphaticdisulfonic acid anhydrides or sulfonamide derivatives thereof and cationically-sensitive monomers, and a process for using cyclic perfluoroaliphaticdisulfonic acid anhydrides or sulfonamide derivatives thereof as catalysts for the cure of cationically-sensitive monomers.

TECHNICAL FIELD

This invention relates to cyclic fluorocarbon anhydrides, sulfonamidederivatives thereof, and a process for their synthesis. In anotheraspect, this invention relates to curable compositions containingcationically-sensitive monomers, such as epoxides, and said cyclicfluorocarbon anhydrides or sulfonamide derivatives thereof. In yetanother aspect, this invention relates to a process for curingcationically-sensitive monomers, utilizing as catalyst said cyclicfluorocarbon anhydrides or sulfonamide derivatives thereof.

BACKGROUND ART

Processes of polymerizing and curing cationically-sensitive monomerssuch as cyclic ethers (e.g., epoxides), vinyl ethers, and N-vinylcompounds, in the presence of catalysts, specifically Lewis acids, suchas boron trifluoride, aluminum chloride, and the like, are well known.However, many of these catalysts are highly corrosive to varioussubstrates such as metals. Other known catalysts for the polymerizationof cationically-sensitive monomers are undesirably toxic. Further, manyof these acid catalysts rapidly catalyze the polymerization of themonomers with which they are admixed and cannot be used where a definiteor prolonged shelf life and/or pot life is desired or required. Thoughsome of these prior art acid catalysts can be used in a latent form,e.g. BF₃.NH₂ C₂ H₅, their latency is affected by moisture and prolongedlatency is difficult to achieve; in addition, when these latentcatalysts are activated, this gives rise to the aforementionedobjectionable corrosiveness. Also, many known catalysts are noteffective for polymerization of a broad range of cationically-sensitivemonomers, e.g., for polymerization of both epoxides and cyclicsiloxanes.

Various linear perfluoroaliphaticsulfonic acid anhydrides of the formula(RSO₂)₂ O, where R is perfluoroalkyl, are described in U.S. Pat. No.2,732,398. U.K. Patent Specification No. 1,120,304 discloses the use ofthe anhydride of trifluoromethanesulfonic acid as a catalyst for use inthe polymerization of various cationically-sensitive monomers.

The utility of linear fluorocarbon sulfonic acid anhydrides (e.g., thosederived from monofunctional perfluoroaliphaticsulfonic acids) asperfluoroaliphaticsulfonylation or acylation agents is also known. Useof the anhydride (CF₃ SO₂)₂ O as a trifluoromethanesulfonylation agentfor formation of trifluoromethanesulfonamides by reaction with ammoniaor amines is disclosed in Chemical Reviews, 77, 69-92 (1977). T. R.Forbus and J. C. Martin, J. Org. Chem., 44, 313 (1979) have disclosedthe preparation of the mixed anhydride, CF₃ SO₂ OC(O)CF₃, and its use asa trifluoroacetylation reagent for aromatic compounds. In thesereactions, however, the above linear anhydrides produce not only thedesired trifluoromethanesulfonylation or acylation product but alsoproduce an equivalent amount of trifluoromethanesulfonic acid or saltthereof as by-product. For example, the reaction of (CF₃ SO₂)₂ O withammonia provides trifluoromethanesulfonamide and an equivalent amount ofthe ammonium salt of trifluoromethanesulfonic acid as by-product. Suchby-product is undesirable because of unfavorable economics in thepreparation of the desired product.

Cyclic fluorocarbon acid anhydrides are highly desirable compositionssince, in contrast to the above linear anhydrides, reaction of cyclicanhydrides with reagents such as ammonia or amines can produce usefuldifunctional products by ring-opening reactions without formation of theabove-described undesirable by-products. Very few such cyclic anhydridesare known, however, because of many factors such as ring instability, ordecomposition, e.g., decarboxylation, during the process of ringformation, or because of the inability of many difunctional acids toundergo ring closure by dehydration. Cyclic anhydrides such asperfluorosuccinic acid anhydride are well known and provide usefulproducts by ring-opening reactions such as reaction with ammonia toproduce ammonium salts of the perfluorocarboxylic acids containingterminal carboxamido (CONH₂) functional groups. However, such cyclicanhydrides or their amide derivatives do not exhibit the catalyticproperties of the cyclic anhydrides or sulfonamide derivatives of theinvention described below.

The use of ammonia or amine salts of monofunctionalperfluoroaliphaticsulfonic acids as latent catalysts for thepolymerization of cationically-sensitive monomers is well known, seeU.S. Pat. No. 3,842,019 and R. R. Alm, Modern Paint and Coatings,October, 1980, pages 88-92. However, the salts described in thesereferences do not include a second functional group in the molecule(e.g., a sulfonamido group) as found in the ammonium or organoammoniumsalts of this invention.

DISCLOSURE OF INVENTION

The present invention provides, in one aspect, cyclic anhydrides ofperfluoroaliphaticdisulfonic acids, having the formula: ##STR1## whereinR_(f) is perfluoroalkylene having 2 to 5 backbone or catenary carbonatoms or perfluorocycloalkylene having 4 to 7, preferably 6, ring atoms,R_(f) optionally being substituted by one or more, e.g., one to three,straight chain, branched, or cyclic perfluoroalkyl groups of 1 to 12,and preferably 1 to 4 carbon atoms, with R_(f) having a total of up to14 carbon atoms. Preferably R_(f) has the formula --CF₂ --_(m) where mis 2 to 4.

The present invention also provides a process for the preparation byring formation of said cyclic anhydrides of perfluoroaliphaticdisulfonicacids, comprising the steps of:

(a) mixing perfluoroaliphaticdisulfonic acid precursor with excessphosphorus pentoxide;

(b) heating the resulting mixture to dehydrate and cyclize saidperfluoroaliphaticdisulfonic acid under anhydrous conditions; and

(c) recovering said cyclic anhydride under anhydrous conditions from theresulting reacted mixture.

The invention further provides sulfonamide derivatives of said cyclicanhydrides, which sulfonamides are useful as latent catalysts for thepolymerization of cationically-sensitive monomers. Said sulfonamides areprepared by reacting one or more of said cyclic anhydrides ofperfluoroaliphaticdisulfonic acids with one or more protonic nitrogenousbase having a pK_(b) of less than about 13.2. The preferred sulfonamideshave the formula:

    R.sup.1 R.sup.2 NSO.sub.2 R.sub.f SO.sub.3.sup.- H.sub.2 N.sup.+ R.sup.1 R.sup.2                                                   II

wherein R_(f) is as defined above, and each R¹ and R² is independentlyhydrogen, or a monovalent organic radical (preferably alkyl, alkoxy,alkenyl, cycloalkyl, aryl, or aryloxy, having 1 to 10 carbon atoms)which can be the same as or different from any other R¹ or R², or eachR¹ and R² bonded to the same N atom can combine with one another to forma cyclic structure containing the N atom, and R¹ and R² can contain from1 to about 20 carbon atoms, can be straight chain, branched or cyclic,can be saturated, unsaturated or aromatic, can contain skeletal orcatenary hetero atoms, i.e., atoms other than carbon (e.g., oxygen orsulfur), and can be unsubstituted or substituted with non-interferingmoieties, i.e., moieties which do not interfere with the functioning ofsaid sulfonamides as latent acid catalysts.

This invention also provides curable compositions, comprisingcationically-sensitive monomers and a catalytically effective amount ofsaid cyclic perfluoroaliphaticdisulfonic acid anhydride or saidsulfonamide derivative thereof.

This invention also provides a process for the polymerization ofcationically-sensitive monomers, comprising the steps of:

(a) mixing with said monomers a catalytically effective amount of saidcyclic perfluoroaliphaticdisulfonic acid anhydride or said sulfonamidederivative thereof, thereby forming a mixture, and

(b) allowing said mixture to polymerize, or heating said mixture toeffect polymerization thereof.

DETAILED DESCRIPTION

In the practice of the present invention, said cyclic anhydrides ofperfluoroaliphaticdisulfonic acids (hereinafter, for brevity, alsodesignated as cyclic anhydrides) are preferably prepared by thedehydration and cyclization of the precursor hydratedperfluoroaliphaticdisulfonic acids (III, below), caused by heating theprecursor acid in the presence of an excess of a suitable dehydratingagent, e.g., phosphorus pentoxide, as shown in Equation 1 below, at atemperature sufficient to provide efficient and controllable reactionbetween the precursor acid and phosphorus pentoxide. Such temperature ispreferably about 100° to 180° C. ##STR2## The resulting cyclic anhydrideproduct is volatile and can be collected by distillation. The cyclicanhydride is prepared and stored under anhydrous conditions.

The amount of phosphorus pentoxide can vary depending on the amount ofwater of hydration present in the precursor perfluoroaliphaticdisulfonicacid hydrate. Generally, a one mole excess of phosphorus pentoxide isused with anhydrous precursor acid, but greater amounts such as up to aten mole excess of more can be used with hydrates of the precursor acid.

An inert diluent such as sand, glass beads, or a high boilingfluorinated organic liquid is usually employed in the dehydration andcyclization reaction. The use of inert, fluorinated organic liquiddiluent, having a boiling point which is substantially higher (e.g., 50°C.) than the boiling point of the desired cyclic anhydride product ispreferred since such a diluent facilitates intimate contact of thereactants, efficient stirring, and good heat transfer, thus aiding inthe rapid completion of the dehydration and cyclization reaction.

When fluorinated diluent is used, the volatile cyclic anhydride productscan be isolated most conveniently on a small scale by purging the heatedreaction flask with nitrogen gas and condensing the anhydride in areceiver cooled with "Dry Ice" to -78° C. Alternatively, the reactionmixture can be subjected to distillation.

The crude cyclic anhydride, obtained by any of the above procedures, canbe additionally purified by redistillation, or can be used directly asan intermediate in the preparation of said sulfonamide derivatives. Thecyclic anhydride should be stored in a sealed dry vessel to avoidhydrolysis through contact with water or water vapor until it is neededfor use as a catalyst or for the preparation of sulfonamide derivatives.The presence of water or water vapor can cause the cyclic anhydride tohydrolyze and form the precursor linear acid hydrate.

The perfluoroaliphaticdisulfonic acid precursors for the preparation ofthe cyclic anhydrides of this invention can be obtained by means of aseries of reactions, starting with the conversion of aliphaticdisulfonylfluorides, R_(h) (SO₂ F)₂ (where R_(h) is the hydrocarbon analog of saidR_(f) radical) to the corresponding perfluoroaliphaticdisulfonylfluorides, R_(f) (SO₂ F)₂, by electrochemical fluorination in anhydroushydrogen fluoride in accordance with the procedure described in U.S.Pat. No. 2,732,398. Alkaline hydrolysis of saidperfluoroaliphaticdisulfonyl fluoride is performed by gradual additionthereof to a stirred solution of aqueous metal base such as carbonate orhydroxide of a metal such as sodium or potassium. Stirring is continueduntil completion of the reaction, followed by collection of theresulting solid salt product, rinsing of the salt with a small amount ofcold water, and drying. The recovered product, R_(f) (SO₃ M)₂ (where Mis for example, Na or K), is dissolved in water, and the resultingsolution is placed on a column of cationic ion exchange resin in theacid form (e.g., "Amberlite IR-120", commercially available from Rohm &Haas, Inc.). The column is eluted with distilled or deionized water, andthe eluate is concentrated under reduced pressure at about 50° C. toconstant weight to yield the desired acid hydrate precursor for thepreparation of said cyclic anhydrides of Formula I, above.

Representative cyclic perfluoroaliphaticdisulfonic acid anhydrides ofthis invention include the following compounds: ##STR3##

The sulfonamide derivatives of the cyclic anhydrides of the inventionare obtained by reaction of the cyclic anhydride with a stoichiometricor excess amount of protonic nitrogenous base having a pk_(b) less thanabout 13.2, such as ammonia, hydrazines, and organic amines containingat least one reactive hydrogen atom attached to nitrogen. The term"hydrazine" as used herein broadly includes hydrazine and hydrazinederivatives in which one or more hydrogen atoms bonded to nitrogen isreplaced with R¹ or R² organic groups. Preferred nitrogenous bases havethe formula HNR¹ R², where R¹ and R² are as defined above. The cyclicanhydrides of this invention are reactive even with weakly basic aminessuch as diphenylamine (which has a pk_(b) of 13.12).

The reaction of the cyclic anhydride with the protonic nitrogenous basecan be carried out at a temperature which provides efficient andcontrolled reaction between the cyclic anhydride and nitrogenous base.Such temperature is generally about -30° to 150° C., depending on thereactivity of the nitrogenous base. The reaction usually occurs readilyat room temperature, with cooling sometimes being desirable to controlthe exotherm. The reactants can be combined in any order but a preferredmethod of conducting the amide formation reaction is by the slowaddition of ammonia or amine to a stirred, cold (e.g., 0° C. to 10° C.)solution of the cyclic anhydride in an anhydrous inert solvent such asmethylene chloride. Other suitable inert solvents include diethyl ether,isopropyl ether, and acetonitrile. The sulfonamide derivative is a saltin the form of an oil, grease, or solid. The oily or greasy salts arepurified by decanting or evaporation of solvent. The solid salts can beisolated by filtration and purified by crystallization from anappropriate solvent or solvent mixture. Preferred sulfonamidederivatives are obtained by the reaction of the cyclic anhydride withammonia or a primary or secondary organic amine.

Representative organic radicals R¹ or R² include methyl, ethyl, butyl,dodecyl, octadecyl, phenyl, o-tolyl, cyclopentyl, cyclohexyl, isopropyl,2-ethylhexyl, propenyl, 2-butenyl, methoxymethyl, methoxyethyl,ethoxyethyl, ethoxybutyl, 4-methoxyphenyl, and eththioethyl. R¹ and R²together with N can be, for example, N-piperidyl or N-pyrrolidyl.

Representative organic amines having a pk_(b) of about 13.2 or less andthe formula NHR¹ R² are described in "Handbook of Chemistry andPhysics", 47th Edition, D-85 (1966-1967). Examples include methylamine,n-butylamine, n-octylamine, isobutylamine, cyclohexylamine,diethylamine, dioctylamine, diisobutylamine, diallylamine, glycine andits ethyl ester, aniline, N-methylaniline, p-chloroaniline,p-cyanoaniline, o-toluidine, m-aminophenol, diphenylamine,alpha-naphthylamine, morpholine, oxazolidine, thiazolidine,p-methoxyaniline, and the like. Such amines can contain substituentgroups which are essentially non-reactive or less reactive than theamino group of the organic amine, including halogen, hydroxy, alkoxy,nitrile, carboxy and carboalkoxy.

Other protonic nitrogenous bases containing more than one basic --NH--or --NH₂ -- group can afford sulfonamide derivatives of this inventionwhich are useful as catalysts. Such derivatives are generally morecomplex than the products represented by Formula II above and can beoligomers or polymers. Such nitrogenous bases include hydrazine,sym-dimethylhydrazine, methylhydrazine, methylhydrazinecarboxylate,guanidine, aminoguanidine, diethylenetriamine, triethylenetetramine,hexamethylenediamine, piperazine, polyethyleneimine, and the like.

Representative simple (i.e., non-oligomeric) sulfonamide derivatives ofthe cyclic anhydrides of this invention include the following:

H₂ NSO₂ CF₂ CF₂ CF₂ SO₃ ⁻ N⁺ H₄,

CH₃ NHSO₂ CF₂ CF₂ CF₂ CF₂ SO₃ ⁻ H₃ N⁺ CH₃,

(C₂ H₅)₂ NSO₂ CF₂ CF₂ SO₃ ⁻ H₂ N⁺ (C₂ H₅)₂,

(HOC₂ H₄)₂ NSO₂ CF₂ CF(C₃ F₇)CF₂ SO₃ ⁻ H₂ N⁺ (C₂ H₄ OH)₂, ##STR4## C₆ H₅N(CH₃)SO₂ CF₂ CF₂ CF₂ SO₃ ⁻ H₂ N⁺ (CH₃)C₆ H₅, ##STR5## (i-C₃ H₇)₂ NSO₂CF₂ CF₂ SO₃ ⁻ H₂ N⁺ (i-C₃ H₇)₂.

The cyclic anhydrides of this invention and sulfonamide derivativesthereof (sometimes collectively referred to hereafter as the compoundsof the invention) are useful for the polymerization or curing ofcationically-sensitive monomers. The term "monomers" as used hereinincludes not only low molecular weight cationically-sensitive materials,but also high molecular weight polymeric compositions, e.g., resinscontaining one or more cationically-sensitive polymerizable groups ofthe types described below, which in the presence of the compounds ofthis invention will undergo polymerization or crosslinking.

Said sulfonamide derivatives of the cyclic anhydrides of this inventionare latent catalysts, particularly with respect to epoxides. The term"latent catalyst" as used herein means a catalyst which does not exhibitor manifest any substantial curing or catalytic effect on monomeradmixed therewith during normal storage or handling of such mixturesuntil the mixture is subjected to heat for the purpose of activation,though some small or otherwise tolerable or insignificant curing of themonomer may take place before activation, as evidenced by a slightincrease in viscosity. Similarly, a composition which has latency or ischaracterized as being latently curable is one which during the periodprior to being heated to effect cure, exhibits little if any gelling,polymerization, etc., though some small or otherwise tolerable orinsignificant curing may take place during such period.

The monomers that can be cured or polymerized with the compounds of thisinvention, using the latter in a catalytically effective amount, arethose known to undergo cationic polymerization and include 1,2-, 1,3-,and 1,4-cyclic ethers (also designated as 1,2-, 1,3-, and 1-4-epoxides),vinyl ethers, N-vinyl compounds, ethylenically unsaturated hydrocarbons,cyclic formals, and cyclic organosiloxanes. An extensive list ofcationically polymerizable monomers which can be used in this inventionare given in U.S. Pat. Nos. 3,347,676 and 3,842.019.

The cyclic ethers which can be polymerized in accordance with thisinvention include those described in "Ring-Opening Polymerizations,"Vol. 2, by Frisch and Reegan, Marcel Dekker, Inc. (1969). Suitable1,2-cyclic ethers are the monomeric and polymeric types of epoxides.They can be aliphatic, cycloaliphatic, aromatic, or heterocyclic andwill typically have an epoxy equivalency of from 1 to 6, preferably 1 to3. Particularly useful are the aliphatic, cycloaliphatic, and glycidylether type 1,2-epoxides such as propylene oxide, epichlorohydrin,styrene oxide, vinylcyclohexene oxide, vinylcyclohexene dioxide,glycidol, butadiene oxide, glycidyl methacrylate, diglycidyl ether ofbisphenol A, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,3,4-epoxy-6-methylcyclohexylmethyl3,4-epoxy-6-methylcyclohexanecarboxylate,bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate, dipentene oxide,epoxidized polybutadiene, 1,4-butanediol diglycidyl ether, polyglycidylether of phenolformaldehyde resole or novolak resin, resorcinoldiglycidyl ether, and epoxy silicones, e.g., dimethylsiloxanes havingcycloaliphatic epoxide or glycidyl ether groups. A wide variety ofcommercial epoxy resins is available and listed in "Handbook of EpoxyResins" by Lee and Neville, McGraw-Hill Book Company, New York (1967)and in "Epoxy Resin Technology" by P. F. Bruins, John Wiley & Sons, NewYork (1968). Representative of the 1,3- and 1,4-cyclic ethers which canbe polymerized in accordance with this invention are oxetane,3,3-bis(chloromethyl)oxetane, and tetrahydrofuran.

Another useful class of cationically-sensitive monomers which can bepolymerized in accordance with this invention is represented by thegeneral formula CH₂ ═C(Y)XR', where X is --O-- or --NR"-- (where R" ishydrogen or lower alkyl), R' is hydrocarbyl, hydrocarbylcarbonyl,halohydrocarbyl, or hydroxyhydrocarbyl when X is oxygen, or R' ishydrocarbyl, hydrocarbylcarbonyl, or hydrocarbylsulfonyl when X isnitrogen, and Y is hydrogen, alkyl, aryl, or other hydrocarbyl, or R'(as hydrocarbylcarbonyl) and R" can be connected to form a 5- or6-membered cyclic structure containing nitrogen as a hetero ring atom.The term "hydrocarbyl" is used herein in its usual sense to mean alkyl,alkenyl, aryl, cycloalkyl, cycloalkenyl, alkaryl, arylalkyl, and thelike. In general, monomers of this type contain a vinyl group and aretypified by vinyl alkyl ethers, such as vinyl methyl ether, vinyl ethylether, vinyl n-butyl ether, vinyl 2-chloroethyl ether, vinyl isobutylether, vinyl phenyl ether and vinyl 2-ethylhexyl ether, vinyl ethers ofsubstituted aliphatic alcohols such as divinyl ether of butanediol,hydroxybutyl vinyl ether, and N-vinyl compounds such as N-vinyl-N-methyloctanesulfonamide and N-vinylpyrrolidone. A description of vinylmonomers and their use in preparing polymers is set forth in "Vinyl andRelated Polymers," by Schildknecht, published by John Wiley & Sons,Inc., New York (1952).

Other cationically-sensitive monomers which can be polymerized in thisinvention include ethylenically unsaturated hydrocarbons such asisobutylene, 1,3-butadiene, isoprene, styrene, and divinylbenzene,especially the vinyl benzenes, cyclic formals such as trioxane,1,3-dioxolane, 2-vinyl-1,3-dioxolane and methyl-1,3-dioxolane, andcyclic siloxanes which can contain various groups attached to thesilicon atom such as a hydrocarbon radical (alkyl, aryl, alkaryl), analkenyl hydrocarbon radical (vinyl, allyl or acryloyloxyalkyl), ahalogenated hydrocarbon radical, a carboxy-containing hydrocarbonradical or ester group, a cyanohydrocarbon radical, hydrogen, halogen ora hydroxy group. Representative cyclic siloxanes arehexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane,phenylheptamethylcyclotetrasiloxane, vinylheptamethylcyclotetrasiloxane,methacryloyloxymethylheptamethylcyclotetrasiloxane,bromomethylheptamethylcyclotetrasiloxane,3-chloropropylheptamethylcyclotetrasiloxane,1,2,3-tris(3,3,3-trifluoropropyl)-1,2,3-trimethylcyclotrisiloxane,acetoxymethylheptamethylcyclotetrasiloxane,cyanomethylheptamethylcyclotetrasiloxane,1,2,3-trihydro-1,2,3-trimethylcyclotrisiloxane, andchloroheptamethylcyclotetrasiloxane. Other known cyclic siloxanes arelisted in "Chemistry and Technology of Silicones" by Walter Noll,Academic Press, New York (1968), Tables 41, 44 and 45.

The cyclic siloxanes can also be polymerized in the presence ofrelatively low molecular weight linear siloxanes such ashexamethyldisiloxane, chloropentamethyldisiloxane andoctamethyltrisiloxane which serve to terminate the growing chain andprovide stable fluids or fluids having reactive end groups.

There is a host of commercially available cationically-sensitivemonomers which can be used in this invention. In particular, cyclicethers which are readily available include propylene oxide, oxetane,epichlorohydrin, tetrahydrofuran, styrene oxide, vinylcyclohexene oxide,glycidol, glycidyl methacrylate, octylene oxide, phenyl glycidyl ether,1,2-butane oxide, diglycidyl ether of bisphenol A (e.g., "Epon 828" and"DER 331"), vinylcyclohexene dioxide (e.g., "ERL-4206"),3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (e.g.,"ERL-4221"),3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate(e.g., "ERL-4201"), bis(3,4-epoxy-6-methylcyclohexylmethyl)-adipate(e.g., "ERL-4289"), aliphatic epoxy modified with polypropylene glycol(e.g., "ERL-4050" and "ERL-4052"), dipentene dioxide (e.g., "ERL-4269"),epoxidized polybutadiene (e.g., "Oxiron 2001"), silicone epoxy (e.g.,"Syl-Kem 90"), 1,4-butanediol diglycidyl ether (e.g., "Araldite RD-2"),polyglycidyl ether of phenolformaldehyde novolak (e.g., "DEN-431,""Epi-Rez 521" and "DEN-438"), resorcinol diglycidyl ether (e.g.,"Kopoxite"), polyglycol diepoxide (e.g., "DER 736"), polyacrylateepoxide (e.g., "Epocryl U-14"), urethane modified epoxide (e.g.,"QX3599"), polyfunctional flexible epoxides (e.g., "Flexibilizer 151"),and mixtures thereof as well as mixtures thereof with co-curatives,curing agents, or hardeners which also are well known (see Lee andNeville and Bruins, supra). Representative of the co-curatives orhardeners which can be used are acid anhydrides such as nadic methylanhydride, cyclopentanetetracarboxylic dianhydride, pyromelliticanhydride, cis-1,2-cyclohexanedicarboxylic anhydride, and mixturesthereof.

In general, the polymerization of cationically-sensitive monomers withthe cyclic anhydrides of this invention can be carried out at roomtemperature for the majority of cationically-sensitive monomers,although low temperature (e.g., -10° C.) or elevated temperatures (e.g.,30° to 200° C., preferably 50° to 100° C.), can be used to either subduethe exotherm of polymerization or to accelerate the polymerization. Inthe case of latent salt catalysts of this invention, temperaturesgenerally in the range of 50° to 250° C., preferably from 80° to 150°C., can be used. The temperature of polymerization and amount ofcatalyst will vary and be dependent on the particularcationically-sensitive monomer used and the desired application of thepolymerized or cured product.

The amount of cyclic anhydride or sulfonamide derivative thereof to beused as a catalyst in this invention (i.e., a catalytically effectiveamount) should be sufficient to effect polymerization of thecationically-sensitive monomer under the desired use conditions. Suchamount generally will be in the range of about 0.01 to 20 weightpercent, preferably 0.5 to 5 weight percent, and most preferably 1 to 2weight percent, based on the weight of cationically-sensitive monomer.

Solvents can be used to assist in dissolution of the cyclic anhydride orsulfonamide derivative thereof in the cationically-sensitive monomer,and are preferred for use with sulfonamide derivatives. Representativesolvents include acetone, methylene chloride, ethyl acetate, methylethyl ketone, acetonitrile, p-dioxane, and the dimethyl ether ofethylene glycol (glyme). In general, in compositions containing cyclicanhydride catalyst, basic solvents or basic impurities in the monomerare avoided to prevent deactivation of the anhydride catalyst.

The curable or polymerizable compositions of this invention, consistingof or consisting essentially of the cationically-sensitive monomer(s)and said cyclic anhydride or sulfonamide derivative thereof as catalyst,can be used for applications like those cationically-sensitive monomersystems cured with other catalysts, such as epoxides cured with BF₃ orthe complex of BF₃ with diethyl ether. Also, curable compositions of theinvention comprising cationically-sensitive monomer(s), said cyclicanhydride or sulfonamide derivative thereof as catalyst, and otheradjuvants (e.g., fillers, reinforcements, pigments, extenders,plasticizers and surface modifying agents) can be prepared in the samemanner as compositions containing cationically-sensitive monomers, othercatalysts, and adjuvants. For example, the curable compositions of thisinvention can be used as adhesives, caulking and sealing compounds,casting and molding compounds, potting and encapsulating compounds,impregnating and coating compounds, etc., depending on the particularmonomers and/or catalyst used. Where the catalyst is used in its latentform, the curable composition can be used as a one-component orcured-in-place system, such capability enhancing its use for theapplications mentioned above. One particular application where suchcapability can be employed is in the electrical arts, where suchlatently curable compositions can be used to coat or impregnate forinsulation or protective purposes electrical motor windings or coils,transformers, capacitors, electrical terminals, cables, and otherelectrical devices.

The curable epoxy composition of this invention can be used to makeshaped articles of self-supporting, structural, filled or reinforcedepoxy resin composites, such as glass fiber cloth reinforced epoxy resincomposites, useful, for example, as repair materials. The variousfillers, reinforcements, and other particulate materials to be mixed orcoated with or dispersed in the curable compositions of this inventionto make the composites of this invention, as well as methods ofprocessing these materials in making the composites, and theirapplications, are those known in the art. In this connection, referenceis made to "Modern Composite Materials," edited by Brautman and Krock,published by Addison-Wesley Publishing Company, Reading, Mass. (1967);and "Handbook of Fiberglass and Advanced Plastics Composites," edited byG. Lubin, published by Van Nostrand Reinhold Company, New York, N.Y.(1969).

The objects and advantages of this invention are further illustrated bythe following examples, but the particular materials and amounts thereofrecited in these examples as well as other conditions and details shouldnot be construed to unduly limit this invention.

EXAMPLE 1

This example shows a general procedure useful for the preparation ofcyclic anhydrides of this invention.

To a 500 ml, three-necked flask fitted with a mechanical stirrer,thermometer, condenser and addition funnel, and containing 54.7 g (0.97mole) of KOH dissolved in 100 ml water, was added gradually over about 1hour, with heating (about 80° C.) and stirring, 63.2 g (0.20 mole) ofhexafluoro-1,3-propanedisulfonyl fluoride, FO₂ SCF₂ CF₂ CF₂ SO₂ F.Heating and stirring were continued for about three more hours and thereaction mixture was allowed to cool overnight. The reaction product wasfiltered, washed with 25 ml of cold water, and allowed to air dry,yielding 78 g of fine, white crystals. Infrared analysis of the crystalswas consistent with the structure hexafluoro-1,3-propanedisulfonic aciddipotassium salt, KO₃ SCF₂ CF₂ CF₂ SO₃ K.

A 9.7 g sample of the salt was dissolved in 50 ml of warm water andplaced in a 50 cm×2.5 cm glass column containing a 20 cm bed of ionexchange resin ("Amberlite IR-120") in the acid (H⁺) form which had beenpreviously prepared by treating the resin with 6 N hydrochloric acid andrinsing with distilled water. The column was eluted with distilledwater. The first 100 ml of eluate were concentrated under reducedpressure to yield 7.5 g of clear liquid product. The identity of theproduct was established by infrared spectroscopy, fluorine NMR (Fnmr)analysis, and water determination, as the hexahydrate ofhexafluoro-1,3-propanedisulfonic acid, HO₃ SCF₂ CF₂ CF₂ SO₃ H.6H₂ O. Theacid hydrate partially crystallized on standing.

A mixture of 11.3 g (0.027 mole) of the above disulfonic acid hydrate(from another run) and 30 g of phosphorus pentoxide was heated to 130°C. under reduced pressure in a flask adapted for short-pathdistillation. A total of 4.3 g colorless liquid product was collected ina trap cooled with "Dry Ice" to -78° C. The liquid product wasredistilled, yielding a colorless, non-fuming liquid with a boilingrange of 109°-110° at atmospheric pressure, n_(D) ²² 1.3562. The productis insoluble in water at room temperature, but hydrolyzes within a fewminutes to give a homogeneous solution. Analytical data are consistentwith the structure hexafluoro-1,3-propanedisulfonic acid anhydride,##STR6##

EXAMPLE 2

This example illustrates the preparation of a sulfonamide derivative ofa cyclic anhydride of this invention.

About 1.0 g of the cyclic hexafluoro-1,3-propanedisulfonic acidanhydride of Example 1 was added dropwise to a stirred 1.0 g portion ofpiperidine which had been cooled to -10° C. The dark crude solid productwas recrystallized from an ethyl acetate/diethyl ether mixture to yieldgold colored crystals, m.p. 86°-88° C.

The structure of the mixed sulfonamide-sulfonate salt, ##STR7## wasestablished by infrared analysis.

EXAMPLE 3

A reaction product with ammonia was prepared by the slow addition ofexcess ammonia gas to an anhydrous methylene chloride solution of thecyclic anhydride prepared in Example 1. The resulting solid product wascrystallized from a mixture of diethyl ether and carbon tetrachloride toyield white crystals, m.p. 168.5°-169° C. Elemental analysis, infraredanalysis, and Fnmr spectra were consistent with the structure:

N⁺ H₄ ⁺ O₃ SCF₂ CF₂ CF₂ SO₂ NH₂.

EXAMPLE 4

This example illustrates another method for carrying out the dehydrationand cyclization reaction of Equation 1, above, utilizing an inert,high-boiling, fluorinated organic diluent.

To a stirred mixture of 30 g of phosphorus pentoxide in 75 ml oftris(perfluoroamyl)amine, (C₅ F₁₁)₃ N, in a 250 ml, three-necked flaskfitted with a thermometer, mechanical stirrer and nitrogen gas inlet,and connected to a trap cooled with "Dry Ice" to -78° C., was added 5.0g of hexafluoro-1,3-propanedisulfonic acid hexahydrate. The resultingmixture was heated over a one hour period to a maximum of 170° C. whilestirring and purging with a slow stream of nitrogen. Warming the -78° C.trap gave a colorless liquid weighing 2.4 g (69% yield). The infraredspectrum was consistent with the desired cyclichexafluoro-1,3-propanedisulfonic acid anhydride.

EXAMPLE 5

Using the method of Example 1, cyclic tetrafluoro-1,2-ethanedisulfonicacid anhydride, ##STR8## b.p. 100° to 101° C., was prepared. Theidentity of the liquid anhydride product was established by infrared andFnmr analysis. The anhydride fumes in moist air, hydrolyzing to form thedisulfonic acid hydrate precursor.

EXAMPLE 6

Using the method of Example 1, cyclic octafluoro-1,4-butanedisulfonicacid anhydride, ##STR9## b.p. 126.5°-127.0° C., was prepared. Thedehydration and cyclization reaction was carried out using sand in thereaction vessel.

EXAMPLE 7

Using the method of Example 1, cyclic decafluoro-1,5-pentanedisulfonicacid anhydride, ##STR10## was prepared. The dehydration and cyclizationreaction was carried out using sand in the reaction vessel.

EXAMPLE 8

A reaction product of the cyclic anhydride of Example 6 with ammonia wasprepared by the gradual addition of ammonia gas to a methylene chloridesolution of the cyclic anhydride. The product was a white powder. Themixed sulfonamide-ammonium salt structure, NH₄ ⁺⁻ O₃ SCF₂ --CF₂ --CF₂--CF₂ --SO₂ NH₂, was established by infrared analysis and Fnmr spectra.

The following examples (9-13) illustrate the utility of cyclicanhydrides of this invention as polymerization catalysts forcationically-sensitive monomers.

EXAMPLE 9 Polymerization of Tetrahydrofuran

In a 500 ml resin flask fitted with mechanical stirrer, thermometer andnitrogen gas inlet was placed 100 g of anhydrous tetrahydrofuran and 15g of cyclohexane. The flask contents were cooled to 4° C. with an icebath, then 2.0 g of hexafluoro-1,3-propanedisulfonic acid anhydride wasadded. A mildly exothermic polymerization reaction ensued, accompaniedby increased viscosity of the reaction mixture. After one hour, the icebath was removed. After three hours, stirring was very difficult.Additional cyclohexane (65 g) and 120 g of toluene were added to thereaction vessel and the resulting solution was mixed with 100 g oftoluene which had been saturated with anhydrous ammonia. The resultingsolution was stirred for one hour at room temperature with 16.7 g ofanion exchange resin ("Amberlite IRA-402", commercially available fromRohm and Hass, Inc.), then filtered to remove the resin particles. Asample of the -NH₂ terminated tetramethylene oxide polymer product, H₂N(C₄ H₈ O)_(n) C₄ H₈ NH₂, was isolated from solution and characterizedby gel permeation chromatrography.

EXAMPLE 10 Polymerization of an Aliphatic Diepoxide

To a small glass vial containing a solution of 2.0 g of3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate ("ERL 4221"epoxide) in 2 ml of methylene chloride was added one drop of the cyclicanhydride of Example 9. A small quantity of solid formed initially, butthere was no apparent viscosity increase after two days at roomtemperature. Heating at about 130° for 10 min. resulted in the formationof a dark, solid resinous product, useful as a potting resin.

EXAMPLE 11 Polymerization of Styrene

To a small glass vial containing a solution of 2.0 g of styrene in 2 mlof methylene chloride was added one drop of the cyclic anhydride ofExample 9. After 0.75 hour, the solution was cloudy. After standingovernight, the solution was very viscous. A clear, tough polymerresulted after several days.

EXAMPLE 12 Polymerization of N-Vinyl Pyrrolidone

Using the method of Example 11, one drop of the cyclic anhydride ofExample 9 was added to a solution of 2.0 g of N-vinyl pyrrolidone in 2ml of methylene chloride. A viscous oil was obtained after four days.

EXAMPLE 13 Polymerization of Octamethylcyclotetrasiloxane

Using the method of Example 11, one drop of the cyclic anhydride ofExample 9 was added to a solution of 2.0 g ofoctamethylcyclotetrasiloxane, [(CH₃)₂ SiO]₄, in 2 ml of methylenechloride. The viscosity of the solution increased overnight. A solidpolymer was obtained after four days.

Examples 14 and 15 show the utility of ammonium and organoammoniumsulfonamidoperfluoroaliphaticsulfonates as latent catalysts for an epoxyresin.

EXAMPLE 14

In a glass vial was placed about 25 mg of H₂ NSO₂ CF₂ CF₂ CF₂ SO₃ ⁻ N⁺H₄ (from Example 3) and 1.0 g "ERL 4221" epoxide. The salt dissolved inthe epoxide at room temperature. There was no apparent change inviscosity of the epoxide/salt solution after 30 hours at roomtemperature, but on heating at 130° for 10 minutes, a clear, nearlycolorless brittle solid formed.

EXAMPLE 15

In a glass vial was placed about 25 mg of CH₃ NHSO₂ CF₂ CF₂ CF₂ SO₃ ⁻ H₂N⁺ CH₃ (prepared using the method of Example 3, but with CH₃ NH₂ inplace of NH₃) and 1.0 g of "ERL 4221" epoxide. The salt dissolved atroom temperature yielding a pale amber solution. There was no apparentreaction or viscosity change after 30 hours at room temperature, but onheating at 130° for 10 minutes, an amber, brittle solid was produced.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

What is claimed is:
 1. Cyclic anhydrides of perfluoroaliphaticdisulfonicacids, having the formula: ##STR11## wherein R_(f) is perfluoroalkylenehaving 2 to 5 catenary carbon atoms or perfluorocycloalkylene having 4to 7 ring atoms, R_(f) optionally being substituted by one or morestraight chain, branched, or cyclic perfluoroalkyl groups of 1 to 12carbon atoms, with R_(f) having a total of up to 14 carbon atoms. 2.Compounds according to claim 1, wherein R_(f) is perfluoroalkylenehaving 2 to 5 catenary carbon atoms, R_(f) optionally being substitutedby one or more straight chain or branched perfluoroalkyl groups of 1 to4 carbon atoms.
 3. Compounds according to claim 1, wherein R_(f) is--CF₂ --_(m) and m is 2 to
 4. 4. A compound according to claim 3,wherein m is
 2. 5. A compound according to claim 3, wherein m is
 3. 6. Acompound according to claim 3, wherein m is 4.